The invention relates to a guide pin assembly for mechanically aligning two units which are designed to function together.
Typically, one unit is aligned with another unit by fitting two or more guide pins mounted on the first unit with the bores of guide bushings mounted on the second unit. However, because of routine manufacturing tolerances, which frequently are as broad as possible in order to minimize manufacturing costs, the guide pin diameter or the bore diameter may be slightly undersized or oversized or they may be slightly off-center. Thus, the two units may not easily fit together or may not snugly fit together. In addition, guide pin assemblies are usually not standardized. Thus, otherwise interchangeable units may in fact not be readily substituted for each other because of customized guide pin assembly designs. There are virtually an unlimited number of combination of guide pin diameters and lengths, tip radii, hex size (if not round), thread size and the like.
These alignment difficulties cause considerable losses in time and not insignificant additional costs in installing, removing, testing and replacing packaged units and other articles with their associated equipment. For example, avionics packages, are routinely installed on equipment racks in aircraft, periodically removed and tested on fixtures, and then eventually replaced on the equipment racks. Although such packages are virtually identical from a functional standpoint, it is to be expected that they will be manufactured over the years on different contracts and so the guide pins or guide bushings will be at least slightly different. Thus, it will be difficult, as a practical matter, to have to test and replace at least some packages, if only because guide pin assemblies or adapters may have to be designed and precision machined. In addition, customized test fixtures may be needed to test the different packages that will be employed on different aircraft.